The relationship between genes and behavior is unknown. We plan to explore this problem by genetically analyzing the anatomically simple egg-laying system of the small soil nematode Caenorhabditis elegans. C. elegans is eminently suited for genetics and much is known about the structure and development of its egg-laying system. Our long-range goal is to understand both how the egg-laying system works and how genes control its structure, function and development. Our major approach will be the isolation and characterization of mutants that effect egg-laying. These mutants should define both the components of the egg-laying system and the genes that affect it. The pleiotropies of these mutants should reveal the general nature of the partitioning of the genetic program controlling egg-laying. Detailed studies of certain mutants, such as those affecting the single essential class of synapse in the egg-laying system, should increase our understanding of how nervous system complexity is specified in the genome; for example, we hope to identify all genes that affect this synapse and to determine what other synapses are affected by each such gene. Biochemical analyses of certain mutants may reveal the molecular bases of how mutations can affect behavior.